The present disclosure relates to an electric contact and a connector terminal pair, and more specifically relates to an electric contact having a coating layer containing silver as a main component on a surface of contact portions that come into electrical contact with each other, and a connector terminal pair having such an electric contact.
A silver plated terminal is sometimes used in an automobile as a connector terminal for large current. The silver plated terminal has excellent heat resistance, corrosion resistance, and electroconductivity, but silver is soft and thus the silver plated terminal has a property of tending to undergo adhesion, resulting in surface abrasion when the terminal is slid in and out. If the silver plating layer is partially removed due to abrasion and the metal of a lower layer such as a base material or a primer plating layer is exposed, the connection reliability of the terminal contact portion will decrease.
As one measure for suppressing abrasion at the time of sliding in the silver plated terminal, a surface of the silver plating layer is provided with an organic film in some cases. For example, in JP 2009-170416A, by providing the surface of an electric contact material made of noble metal such as silver with two organic films made of a specific organic compound, a reduction in the dynamic frictional coefficient of the surface and suppress abrasion is achieved.
Also, even in a case where a silver alloy layer is provided as a lower layer of the silver layer, suppression of abrasion on the surface of the silver layer can be achieved due to the effects of the composition and the organizational structure of the silver alloy layer while utilizing the high heat resistance, corrosion resistance, and electroconductivity of silver. For example, as disclosed in JP 2013-231228A filed by the present applicants, forming a layer structure in which the surface of a hard silver-tin alloy layer is coated with a soft silver coating layer of the electric contact of the connector terminal makes it possible to reduce the frictional coefficient of the electric contact. Abrasion of the silver can be suppressed by reducing the frictional coefficient.
Moreover, WO 2015/083547 filed by the present applicants discloses use of an embossed contact having a layer structure constituted by a silver-tin alloy layer and a silver coating layer as in JP 2013-231228A as an electric contact obtained by combing the embossed contact with a plate-shaped contact coated with a silver layer that does not have the silver-tin alloy layer directly below. Adopting such a combination makes it possible to reduce the frictional coefficient and to reduce the contact resistance of the surface when the electric contact undergoes abrasion.